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Full text of "The Cambridge Natural History"

xv                       HAMSTERS   AND   COTTON   RATS                    4/9
hordes so familiar (as far as their, description is concerned) to
everybody. The Lemmings do not return from their exodus.
They die from various causes, including combats with one
another. Their chief foes, however, are Wolves and G-luttons,
Buzzards and Havens, Owls and Skuas, which batten on the
migrant hordes. Their sudden increase in numbers recalls the
similar increase at times of the Field-Vole, to which reference
has already been made.
JSlloMiLs is an Old-World genus, which leads a ** Talpine " life,
and has in consequence rudimentary external ears and very
small eyes. The tail is short. Contrary to what might be
expected from its mode of life, the claws upon the digits are
not strong.
The remaining genera of Vole-like Murines are Phenacomys
and Syn.aptQ'mys from North America, and Siphneiis from Palae-
arctic Asia. ISvotomys is one of those genera which are common
to both the Palaearctic and the Nearctic regions, but the bulk of
the species are North American.
Sub-Fain. 9. Bi^modontinae.—This is the name given to
another sub-family of Murine Rodents, a group which includes
the Hamsters in the Old World as well as a large number of
South American genera of Rat-like animals. Of these latter
there are a very large number, the bulk of the group being
American.
The Hamsters, genus Cricetus, as it is usually called, although
apparently the correct name is Hamster, are Old-World forms of
Pouched itats. The Common Hamster, O. frumentari'us, is about
210 inm. long, with a tail of 58 mm. It has cheek pouches.
The small and the large intestines ,are not very unequal in
length, and the caecum is fairly large, being about one-sixth to
one-seventh of the length of either. It is a purely vegetable-
feeding creature, and in Germany where it occurs (and from
which language its vernacular name is derived), hibernates during
the winter in its burrow, having previously surrounded itself
with a great accumulation of food carried thither.
To North America are peculiar the genera Ofiychomys, Sig-
tnodon, and JPerowigseus. The genus Sigmodon, the Cotton Rats,
reaches Central America, and even gets a little farther south.
The other two genera, though mainly North American, also
extend their range to the south, Onycfaomys has hairy foot-